Method for directed self-assembly lithography

Abstract

The invention relates to a method of directional self-assembly lithography, said method comprising a step of depositing a block copolymer film on a layer ( 20 ) neutral with respect the block copolymer, said block copolymer film being for use as a lithography mask, said method being characterized in that it comprises the following steps of: depositing said neutral layer ( 20 ) on a surface of a substrate ( 10 ), said neutral layer ( 20 ) being of the carbon or fluoro-carbon type deposited to a thickness greater than 1.5 times the thickness of the block copolymer film ( 40 ), crosslinking said neutral layer, depositing said block copolymer film, comprising at least one silylated block, on said crosslinked neutral layer ( 30 ), subjecting the stack to an assembly temperature in order to nanostructure said block copolymer, removing (G 1 ) at least one of the nano-domains ( 41, 42 ) from the nanostructured block copolymer film ( 40 ), in order to create a pattern intended to be transferred by etching (G 2 , G 3 , G 4 ) into the thickness of the substrate ( 10 ).

1 . A directed self-assembly lithography method, said method comprising a step of depositing a block copolymer film on a layer neutral with respect to each block of the block copolymer, said block copolymer film being for use as a lithography mask, said lithography method comprising the following steps of:
 depositing said neutral layer directly on a surface of a substrate, said neutral layer being of a carbon or fluoro-carbon type (n-SOC) deposited to a thickness greater than 1.5 times a thickness of said block copolymer film,   crosslinking all or part of said carbon or fluoro-carbon neutral layer,   depositing said block copolymer film on said crosslinked carbon or fluoro-carbon neutral layer, said block copolymer comprising at least one silylated block,   subjecting the stack of layers thus created to an assembly temperature in order to nanostructure said block copolymer,   removing at least one nano-domain from said nanostructured block copolymer, in order to create a pattern intended to be transferred by etching into the carbon or fluoro-carbon neutral layer, and then into a thickness of the underlying substrate.   
     
     
         2 . The lithography method according to  claim 1 , wherein the carbon or fluoro-carbon neutral layer comprises reactive groups of an epoxy type and/or unsaturations in its polymer chain either directly in a body of the polymer chain itself, or as a pendant group therein. 
     
     
         3 . The lithography method according to  claim 2 , wherein a minimum rate of reactive groups of the epoxy type and/or of unsaturations in the polymer chain of the carbon or fluoro-carbon neutral layer is 10% and 70%. 
     
     
         4 . The lithography method according to  claim 1 , wherein the carbon or fluoro-carbon neutral layer further comprises a latent crosslinking agent selected from derivatives of an organic peroxide type, or derivatives having a chemical function of an azo type, or derivatives of an alkyl halide type, or chemical derivatives for generating a thermally activated acid proton selected from among: ammonium salts, pyridinium salts, phosphoric or sulfuric or sulfonic acids, onium salts, imidazolium salts, photo-generated acids and photo-generated bases. 
     
     
         5 . The lithography method according to  claim 1 , wherein the carbon or fluoro-carbon neutral layer has, in whole or in part, a chemical structure of an acrylate or methacrylate type based on comonomers selected from among: hydroxyalkyl acrylates, glycidyl acrylates, dicyclopentenyloxyethyl acrylates, fluorinated methacrylates, tert-butyl acrylates, methacrylates, and mixtures of at least two of the aforementioned comonomers. 
     
     
         6 . The lithography method according to  claim 1 , wherein the carbon or fluoro-carbon neutral layer comprises hydroxy groups promoting its solubility in polar solvents selected from at least one of the following solvents or solvent mixtures: MIBK, methanol, isopropanol, PGME, ethanol, PGMEA, ethyl lactate, cyclohexanone, cyclopentanone, anisole, alkyl acetate, n-butyl acetate, iso-amyl acetate. 
     
     
         7 . The lithography method according to  claim 1 , wherein the carbon or fluoro-carbon neutral layer comprises at least three co-monomers of a glycidyl (meth)acrylate type (G), a hydroxyalkyl (meth)acrylate (H) type, and a fluoroalkyl (meth)acrylate (F) type, and wherein a proportion of each said monomer G, H, F is between 10 and 90% by weight, with a sum of the 3 monomers being equal to 100%. 
     
     
         8 . The lithography method according to  claim 1 , further comprising a step of depositing a third layer on a surface of the block copolymer, such that prior to the step of nano-structuring the block copolymer film, said third layer is crosslinked in whole or in part. 
     
     
         9 . The lithography method according to the  claim 8 , wherein the third layer comprises a latent crosslinking agent selected from: a chemical derivatives for generating a thermally activated acid proton selected from among: ammonium salts, onium salts, sulfonium salts, phosphonium or imidazolium salts, a photo-generated acid (PAG), and a photo-generated base (PBG). 
     
     
         10 . The lithography method according to  claim 1 , wherein the step of crosslinking the carbon or fluoro-carbon neutral layer (n-SOC) and/or the third layer is carried out by light irradiation, exposure to self-thermalization, electrochemical process, plasma, ion bombardment, electron beam, mechanical stress, exposure to a chemical species, or any combination of the aforementioned techniques. 
     
     
         11 . The lithography method according to  claim 10 , wherein the step of crosslinking the carbon or fluoro-carbon neutral layer is carried out by exposure to thermalization, at a temperature between 100 and 300° C. for a period of less than or equal to 15 minutes. 
     
     
         12 . The lithography method according to  claim 1 , wherein a pattern can be drawn in the neutral layer by exposure to light radiation or an electron beam. 
     
     
         13 . The lithography method according to one of  claim 8 , wherein a pattern can be drawn in the third layer, by exposure to light radiation or an electron beam. 
     
     
         14 . The lithography method according to  claim 12 , wherein when the pattern is drawn by exposure to light radiation, at least the carbon or fluoro-carbon neutral and the block copolymer have anti-reflection properties. 
     
     
         15 . The lithography method according to  claim 12 , wherein when the pattern is drawn by exposure to light radiation, a bottom anti-reflection coating is dispensed on the substrate, prior to the deposition of said carbon or fluoro-carbon neutral layer. 
     
     
         16 . The lithography method according to  claim 1 , wherein the step of depositing the neutral layer directly on the surface of the subtract comprises a direct contact between said neutral layer and the substrate. 
     
     
         17 . The lithography method according to  claim 1 , wherein the step of depositing the block copolymer film on the crosslinked carbon or fluoro-carbon neutral layer comprises a direct contact between said crosslinked carbon or fluoro-carbon neutral layer and the block copolymer film. 
     
     
         18 . The lithography method according to  claim 1 , wherein said lithography method excludes use of intermediate layer such as Si-ARC/SOG, SOC, and neutral layer. 
     
     
         19 . Lithography stack obtained by a directed self-assembly lithography method, said stack comprising a substrate to a surface of which is deposited a neutral layer, said neutral layer being covered by a block copolymer film, said block copolymer film being for use as a lithography mask, and said neutral layer being neutral with respect to each of block of the block copolymer, wherein the neutral layer is in direct contact with the underlying substrate, the neutral layer being of a carbon or fluoro-carbon type (n-SOC), crosslinked in whole or in part, deposited to a thickness greater than 1.5 times a thickness of said block copolymer film, said block copolymer film comprising at least one silylated block, and being in direct contact with said crosslinked carbon or fluoro-carbon neutral layer, said block copolymer film having been nanostructured by treatment at an assembly temperature and being a discontinuous film, in order to create a pattern capable of being transferred by etching in the carbon or fluoro-carbon neutral layer then in the thickness of the underlying substrate. 
     
     
         20 . Method according to  claim 1 , wherein a lithography mask intended to allow the etching of patterns at depths between 10 nm and 400 nm is thereby manufactured.